Investigation of the latent heat associated with the solidification of an Al-TiB2 composite

Differential scanning calorimetry was used to measure the latent heat evolved or absorbed during solidification or melting of a composite made from commercial-purity aluminium reinforced with TiB2 particulate. The measured latent heat was up to 10% less than that expected assuming a rule of mixtures. The analysis of the particles revealed that up to 20 at.% of Ti is substituted by Al in the boride. The concomitant increase in volume fraction of particulate (Al3Ti) and the associated reduction in Al accounted for the latent heat discrepancy. It was previously suggested that strain energy could explain the discrepancy; however, X-ray and neutron diffraction stress measurements showed that this is unlikely.